<?php
$str = "i want to fly, Fly in the sky ,fly to the Higher!";
echo strtoupper( $str ) . "<br>";
echo strtolower( $str ) . "<br>";
echo ucfirst( $str ) . "<br>";
echo ucwords( $str ) . "<br>";
//替换字符串中内容
$abc = 'javascript';
echo str_replace( 'a', 'b', $abc );








